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<br />c.c <br />~ <br />c. <br />C""; <br /> <br />c~ <br />"~~ <br />'''t~~ <br /> <br />PART I <br />THE DISASTER <br /> <br />Exceedingly large amounts of runoff caused by rapidly melting <br />snow from record snowfalls and late rains this past winter <br />and spring resulted in unusually high volumes of water entering <br />the Colorado River basin (for a detailed description of the <br />meteorological and hydrological conditions preceeding the <br />flood event, see Appendix B and for information on inflows, <br />releases, and water surface elevations at the various reser- <br />voirs, see Appendix C). These extraordinary amounts of water <br />required Glen Canyon, Hoover, Davis, and Parker Dams to release <br />unprecedented volumes of water into the lower Colorado River <br />system. The releases have caused the Colorado River to flood <br />low-lying areas, erode river banks, and raise adjacent ground- <br />water levels. Initial releases from Hoover Dam resulted in <br />downstream flooding to areas built within the 100-year flood <br />plain. Stabilization of releases between 38.000 cfs and 42.000 <br />cfs has reduced the potential for the river to rise further <br />but will probably result in flood waters remaining at their <br />current levels for 3 to 6 months. This situation could worsen <br />if thunderstorms cause flash flooding or residual tropical <br />storms occur over the region this summer. Flood damage to <br />urban and agricultural lands extend from Davis Dam on the <br />north to the Mexican border, an approximate distance of ~ <br />miles. Groundwater seepaqe causinq surface pondin~ has been <br />observed up to three miles inland from the Colorado River. <br /> <br />Areas south of Davis Dam experienced the greatest incidents of <br />damage and economic loss. Flooding occurred in low lying <br />developments built in the floodplain and adjacent marsh lands. <br />Many buildings downstream from Davis Dam are currently inundated <br />and are likely to remain flooded for many months. The initial <br />surge of flood waters swept away docks and boat facilities and <br />some unstable trees along the river bank, generating waterborne <br />debris. <br /> <br />Damage to recreational facilities is widespread, affecting <br />beaches, campsites, boat docks, launchsites, and businesses <br />servicing these activities. <br /> <br />Waste water (septic) systems and water treatment (potable) <br />systems were also damaged and will probably present long <br />term problems. <br /> <br />High groundwater is a major problem in many areas along the <br />river, with the Yuma area experiencing current and potentially <br />long term problems. There is evidence of rising groundwater <br />softening the Giss Parkway (1-8) roadbed. Water seepage is <br />also evident near homes located close to the levee on Yuma's <br />east side. <br /> <br />4 <br />